Parking lock control device for vehicle and control method

ABSTRACT

In a parking lock control device of a vehicle of the present invention, when a parking lock activation command is outputted, either one of parking lock mechanisms is activated. In this state, a movement of the vehicle is estimated or detected, and when the vehicle movement is a predetermined amount or more, the parking lock control device generates a torque that suppresses the vehicle movement by the motor connected to the other parking lock mechanism. Power consumption associated with the parking lock is then suppressed.

TECHNICAL FIELD

The present invention relates to a parking lock control device thatlocks a wheel.

BACKGROUND ART

A related art of a Patent Document 1 has disclosed a configuration inwhich, in a vehicle having a motor for each wheel, a parking lockmechanism is provided at each wheel, and when a parking lock request isoutputted, by activating the parking lock mechanism of each wheel, thewheel is locked.

However, in a case where a plurality of parking lock mechanisms areactivated, there arises a problem that increases power consumption.

CITATION LIST Patent Document

Patent Document 1: Japanese Patent Provisional publication Tokkai No.2007-314036

SUMMARY OF THE INVENTION

An object of the present invention is to provide a parking lock controldevice for the vehicle, which is capable of suppressing the powerconsumption.

In the parking lock control device for the vehicle of the presentinvention, when a parking lock activation command is outputted, eitherone of parking lock mechanisms is activated. And also, a movement of thevehicle is estimated or detected, then when the vehicle moves apredetermined amount or more, a torque that suppresses the vehiclemovement is generated by the motor connected to the other parking lockmechanism.

Accordingly, especially in a case where the vehicle does not move, byactivating only one parking lock mechanism, the power consumption can besuppressed, and a travel distance can be made longer. Further, in astate in which only the one parking lock mechanism is activated, whenthe vehicle moves, the vehicle movement is suppressed by the motor.Therefore, the vehicle movement can be suppressed under all conditions.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a general system diagram of a vehicle that is provided with aparking lock control device of an embodiment of the present invention.

FIG. 2 is a flow chart showing a parking lock mechanism control processexecuted in a parking lock controller of the embodiment.

FIGS. 3A, 3B and 3C are schematic diagrams for explaining one wheel/bothwheels lock determination process of the embodiment.

FIG. 4 is a schematic diagram showing a movement of the vehicle by anactivation of the parking lock mechanism in a case where wheels of thevehicle are turned to a left hand side, of the embodiment.

FIGS. 5A and 5B are schematic diagrams showing a vehicle movementjudgment process of the embodiment.

FIG. 6 is a flow chart for operating a drive motor when outputting anactivation command to an unlocked side parking lock mechanism on thebasis of a motor rotation speed, of the embodiment.

FIG. 7 is time charts for operating the drive motor when outputting theactivation command to the unlocked side parking lock mechanism, of theembodiment.

FIG. 8 is a flow chart for operating the drive motor when outputting theactivation command to the unlocked side parking lock mechanism on thebasis of a cumulative motor rotation speed, of the embodiment.

FIG. 9 is time charts for operating the drive motor when outputting theactivation command to the unlocked side parking lock mechanism on thebasis of the cumulative motor rotation speed, of the embodiment.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is a general system diagram of a vehicle that is provided with aparking lock control device of an embodiment of the present invention.The vehicle of the present embodiment is a rear wheel drive typeelectric vehicle, and has front wheels FR, FL that are driven wheels andrear wheels RR, RL that are driving wheels.

The rear wheel RR on a right side of the vehicle is provided with anin-wheel type drive motor MR (a right side motor) that directly drivesthis rear wheel RR, a parking lock mechanism PLR that can stop anrotation axis of the drive motor MR by connecting the rotation axis ofthe drive motor MR to a vehicle body side and a resolver NR (a vehiclebehavior detecting unit) that detects a rotation speed (or a rotationangle) of the drive motor MR. Likewise, the rear wheel RL on a left sideof the vehicle is provided with an in-wheel type drive motor ML (a leftside motor) that directly drives this rear wheel RL, a parking lockmechanism PLL that can stop an rotation axis of the drive motor ML byconnecting the rotation axis of the drive motor ML to the vehicle bodyside and a receiver NL (the vehicle behavior detecting unit) thatdetects a rotation speed (or a rotation angle) of the drive motor ML.

Each of the parking lock mechanisms PLR, PLL is a mechanism that locksthe rotation by the fact that a parking pole is engaged with a parkinggear. The parking pole is configured to be actuated by anelectromagnetic actuator. The electromagnetic parking lock mechanism isa well-known technique, its detailed explanation is therefore omittedhere.

Further, the parking lock control device has an inclination detectingunit 1 (the vehicle behavior detecting unit) that detects an inclinationof the vehicle, a present position detecting unit 2 (the vehiclebehavior detecting unit) that detects a present position and a steeringwheel turning angle detecting unit 3 that detects a turning angle of asteering wheel.

The inclination detecting unit 1 is, for instance, a longitudinal(back-and-forth) G sensor that detects a longitudinal (back-and-forth)acceleration of the vehicle and/or a lateral G sensor that detects alateral (side-to-side) acceleration of the vehicle. The inclinationdetecting unit 1 is configured to not only detect the accelerationacting on a travelling vehicle but also detect an inclination of roadsurface of a place where the vehicle is currently positioned during avehicle stop or almost in a state of the vehicle stop.

The present position detecting unit 2 is, for instance, a navigationsystem using GPS. The present position detecting unit 2 is configured torecognize or realize road surface inclination information etc. of thepresent position.

The steering wheel turning angle detecting unit 3 is a steering anglesensor that detects a steering angle that is an operating amount of asteering wheel 4, and detects a value corresponding to a tire turningangle of the front wheels FR, FL at the present tine point. Here, theother sensor (e.g. a sensor detecting a movement of a rack) that candetect the tire turning angle could to provided.

In addition, the parking lock control device has a parking lockcontroller PLCU. The parking lock controller PLCU outputs an activationcommand to the parking lock mechanisms PLR, PLL on the basis ofinformation of a slope of the road surface where the vehicle ispositioned which is detected by the inclination detecting unit 1, theroad surface inclination information of the present vehicle positionwhich is detected by the present position detecting unit 2, the steeringangle detected by the steering wheel turning angle detecting unit 3 andrear wheel rotation speeds detected by the resolvers NR, NL provided atthe rear wheels RR, RL.

Features of the embodiment will be explained here. As described above,the electric vehicle of the embodiment has the parking lock mechanismsPLR, PLL at the both rear wheels. And it is conceivable that whenactivating the parking lock mechanism, the activation command isoutputted to the both parking lock mechanisms PLR, PLL and the both rearwheels are locked. However, since the electrical actuator is used forthe activation of this parking lock mechanism, power consumption isincreased. Further, in a case where the rear wheels are merely locked ona flat road, if only one wheel is locked without locking the bothwheels, a purpose of forbidding (stopping) movement of the vehicle isachieved.

Therefore, in she embodiment, in a circumstance in which the road isbasically the flat road and even if the vehicle is parked as it is, themovement of the vehicle does not occur, a lock command is outputted toonly the one wheel. With this manner, the power consumed by theelectrical actuator of the parking lock mechanism can be suppressed, andit is possible to increase a travel distance.

Here, as explained above, in the case of the flat road, locking only theone wheel brings no problem. However, if the vehicle is parked with onlythe one wheel locked in a state in which the vehicle is positioned on aninclined road surface (e.g. an inclined parking lot), there is a problemthat the other wheels go round and the vehicle slightly moves with thelocked wheel being a center.

Further, the activation command to the parking lock mechanism isbasically outputted according to a signal generated upon shift of atransmission shift lever to a parking range by driver's shift leveroperation. Thus, the activation command is not necessarily outputtedafter the vehicle stop, but there is a case where the activation commandis outputted and the parking lock mechanism is activated in a state inwhich the vehicle has a slight vehicle speed. At this time, if only theone wheel is locked, there is a problem that the other wheels go roundby inertia of the vehicle with the locked wheel stopped, and the vehiclerotates with the locked wheel being the center, then the vehiclebehavior is unsettled.

Thus, in the embodiment, as a basic control, if the road is the flatroad, the lock command is outputted to only the one wheel. In additionto this control configuration, in a case where there is a risk that thevehicle behavior will be unsettled or the vehicle behavior is actuallyunsettled due to the activation of the one parking lock mechanism, or ina case where there is a risk that the vehicle will move from the vehiclestop state or the vehicle actually moves due to the activation of theone parking lock mechanism, the both parking lock mechanisms areactivated.

In the following description, the control configuration will beexplained.

FIG. 2 is a flow chart showing a parking lock mechanism activationcontrol process executed in the parking lock controller of theembodiment.

At step S1, a judgment is made as to whether or not an activationrequest of the parking lock mechanism is present. If it is judged thatthe activation request of the parking lock mechanism is present, theroutine proceeds to step S2. If it is judged that the activation requestof the parking lock mechanism is not present, this step is repeated.Here, the activation request of the parking lock mechanism indicates acase where the shift lever operated by the driver is positioned at theparking range. Further, even if the parking lock mechanism is activatedduring travel at some speed, since only a so-called ratcheting state inwhich the parking pole is flipped by the parking gear occurs, theactivation request is basically received at any timing. However,depending on other conditions, the activation request of the parkinglock mechanism could be cancelled. These are not especially limited.

At step S2, a determination of one wheel/both wheels lock is made. FIGS.3A, 3B and 3C are schematic diagrams tor explaining one wheel/bothwheels lock determination process of the embodiment. As shown in FIG.3A, in a plane with the longitudinal (back-and-forth) acceleration ofthe vehicle being a vertical axis and the lateral (side-to-side)acceleration of the vehicle being a horizontal axis, a vehicleacceleration area, by which it can be judged that the vehicle does notmove on the sloping or inclined road, is set. Then, a judgment is madeas to whether or not the detected acceleration exists in this area for apredetermined diagnostic time. When judged that the detectedacceleration exists in this area for the predetermined diagnostic time,it is judged that the vehicle does not move on the sloping or inclinedroad (see FIG. 3B). In this case, the routine proceeds to step S5. Onthe other hand, when the acceleration existing outside this area isdetected during the diagnostic time, it is judged that there is a riskthat the vehicle will move on the sloping or inclined road (see FIG.3C). In this case, the routine proceeds to step S3.

Regarding the vehicle acceleration area, a longitudinal accelerationarea could be set to be greater than a lateral acceleration area.Further, the area is set by not only a circle but also a linear-shapedrhombus.

In addition, when judged that the detected acceleration exists outsidethe area even once during the diagnostic time, it could be judged thatthere is a risk that the vehicle will move. Or, when judged that thedetected acceleration continuously exists outside the area for a certaintime, it could be judged that there is a risk that the vehicle willmove.

In a case where the road surface inclination information of the presentvehicle position, detected by the present position detecting unit 2, isthe sloping or inclined road and it is possible to judge that there is arisk that the vehicle will move on the sloping or inclined road due tothe one wheel lock, the routine proceeds to step S3, and the activationcommand is outputted to the both parking lock mechanisms PLR, PLL.

On the other hand, in a case where it is possible to judge that there isno risk that the vehicle moves by the one wheel lock at the presses timepoint, the routine proceeds to step S5.

At step S4, count-up of the number of times each of the right and leftside parking lock mechanisms is activated is done. For instance, whenthe both parking lock mechanisms are activated, both count-ups are done.When the one parking lock mechanism is activated, one count-up is done.

At stop S5, a determination process, which determines the parking lockmechanism to which the parking lock command is outputted, is performed.The parking lock mechanism is determined according to the steering angleand a count-up value of the number of times of the lock.

(Judgment Process According to the Steering Angle)

First, on the basis of the steering angle detected by the steering wheelturning angle detecting unit 3, a steering direction is checked. Then,when judged that the steering wheel is steered or turned to a right handside at a predetermined steering angle or more, the activation commandis outputted to the parking lock mechanism PLL of the rear left wheelRL. When judged that the steering wheel is steered or turned to a lefthand side at a predetermined steering angle or more, the activationcommand is outputted to the parking lock mechanism PLR of the rear rightwheel RR.

Here, the reason for determining which parking lock mechanism isactivated according to the steering angle will be explained.

FIG. 4 is a schematic diagram showing a movement of the vehicle by theactivation of the parking lock mechanism in a case where the wheels ofthe vehicle are steered or turned to a left hand side. It the parkinglock mechanism PLL of the rear left wheel RL is activated with thewheels turned to the left hand side, as shown by “x” in FIG. 4, there isa risk that the vehicle rotates with the rear left wheel RL being thecenter, then the movement of the vehicle can not effectively beforbidden.

In contrast to this, as shown by “o” in FIG. 4, if the parking lockmechanism PLR of the rear right wheel RR is activated, the rotation ofthe vehicle can be inhibited, then the movement of the vehicle caneffectively be forbidden. This also occurs to a case where the wheels ofthe vehicle are steered or turned to a right hand side.

From the foregoing, by determining the parting lock mechanism activatedaccording to the steering angle, the movement of the vehicle caneffectively be suppressed.

(Judgment Process According to the Number of Times of the Lock)

Next, when judged that the steering angle detected by the steering wheelturning angle detecting unit 3 is smaller than a predetermined angle ofthe right or left hand side direction and the steering wheel ispositioned at a substantially neutral position, since there isespecially nothing to choose between the right and the left in terms ofthe vehicle behavior, the right and the left (the parking lock mechanismPLR and the parking lock mechanism PLL) is determined according to eachnumber of times of the lock. This is because in a case where the numberof times of the lock, which is counted at step S4 as mentioned above, isunbalanced and is larger on one side of the right and the left, there isa need to secure durability of the parking gear and the parking pole onthe one side to excess. Thus when judged that the steering angle ispositioned at the substantially neutral angle position, the activationcommend is outputted to the parking lock mechanism whose number of timesof the lock is smaller.

Here, in a case where the steering angle is the predetermined angle orgreater, even if the above judgment process according to the number oftimes of the lock is performed, a judgment result according to thesteering angle is given priority. This is because suppressing themovement of the vehicle is more important than securing the durability.

At step S6, the activation command is outputted to the parking lockmechanism that is determined at step S5.

At step S7, after outputting the activation command of the parking lockmechanism, a judgment is made as to whether or not the vehicle moves. Ifit is judged that there is a risk that the vehicle will move, theroutine proceeds to step S8, and the activation command is outputted toan unlocked side parking lock mechanism. Then the routine proceeds tostep S4, and the count-up of the both parking lock mechanisms is done.

On the other hand, if it is judged that there is no risk that thevehicle will move, the routine proceeds to step S4, and the count-up ofthe activated parking lock mechanism is done.

Here, a judgment after the output of the activation command to theparking lock mechanism will be explained.

First, in the same manner as that at step S2, a judgment is made as towhether or not the detected acceleration exists in the vehicleacceleration area for a predetermined diagnostic time. Although thisjudgment has already been made at step S2, by continuously makingjudgment even when the vehicle stops, even if the vehicle inclines, forinstance, during transport by ferry, the both parking lock mechanismscan be activated.

Next, the rotation speed of each of the right and left wheels isdetected by the resolvers NR, NL, and the movement of the vehicle isjudged according to these rotation speeds.

FIGS. 5A and 5B are schematic diagrams showing a vehicle movementjudgment process of the embodiment. FIG. 5A is time charts forindicating the judgment according to the motor rotation speed or themotor rotation angle. Since the motor rotation speed and the motorrotation angle are substantially the same, in the following description,only the judgment according to the motor rotation speed will beexplained.

If an absolute value of the motor rotation speed is less than apredetermined rotation speed, it is judged that the case of the onewheel lock has no problem. If the absolute value of the motor rotationspeed is the predetermined rotation speed or more, it is judged that theboth-wheel lock is necessary.

Here, the predetermined rotation speed is a motor rotation speed bywhich it can be judged that the vehicle does not move by the slope orthe inclination, and is a predetermined value. In a case where thevehicle moves forward, for instance, the rotation speed is a plus siderotation speed. In a case where the vehicle moves backward, the rotationspeed is a minus side rotation speed. Then, the judgment is made as towhether or not the absolute value of the motor rotation speed is lessthan the predetermined rotation speed. In FIG. 5A, the predeterminedrotation speed is not shown by the absolute value, but is shownincluding signs. That is, the positive side predetermined rotation speedand the negative side predetermined rotation speed are shown.

The resolver detecting the rotation angle which is necessary for themotor control is the one that can detect a slight rotation changetogether with a rotation direction. On the other hand, with regard to awheel speed sensor used for an anti-lock brake control etc., there is acase that the wheel speed sensor can not detect the rotation direction,and also resolution of the wheel speed sensor is lower than that of theresolver. Thus, by employing the resolver, a slight movement of thevehicle and its movement direction can be detected, then a high accuratejudgment can be made.

In an example shown in FIG. 5A, the judgment is made according to howmuch the rotation speed changes during a predetermined diagnostic time.However, the diagnosis could be carried out continuously for thepredetermined diagnostic time, or the diagnosis might be carried out atregular time intervals during the predetermined diagnostic time.

FIG. 5B is time charts for indicating the judgment according to acumulative motor rotation speed.

When the motor rotation speed is totalized and an absolute value of thiscumulative motor rotation speed (i.e. a movement distance) is within arange that is smaller than a predetermined cumulative motor rotationspeed, it is judged that the case of the one wheel lock has no problem.When the absolute value of the cumulative motor rotation speed is thepredetermined cumulative motor rotation speed or greater, it is judgedthat the both-wheel lock is necessary.

The reason why the cumulative motor rotation speed is used is becausewhen the wheel (the vehicle) moves slowly and continuously, there is aneed to lock the both wheels, and also in a case where it is judged, dueto a slight vehicle back-and-forth sway, that the both-wheel lock isnecessary, this redundant judgment is avoided.

With respect to the judgment according to the motor rotation speed andthe judgment according to the cumulative motor rotation speed, the bothjudgments could be made at the same time, or only one of the bothjudgments might be judged.

Here, if it is judged that the vehicle starts to move then theactivation command is outputted to the unlocked side parking lockmechanism and the unlocked side parking lock mechanism is immediatelyactivated, an abrupt change of the acceleration occurs upon theengagement of the parking pole and the parking gear, and consequently,the driver is subject to an odd or awkward feeling. Further, this mightcause decrease in durability of the parking pole and the parking gear.Thus, the change of the rotation speed of the driving wheel issuppressed with torque, which acts on the driving wheel in a directionopposite to a moving direction, outputted by the unlocked side drivemotor, then the parking lock mechanism is activated. The abrupt changeof the acceleration can be therefore suppressed.

In the following description, a control process when activating theunlocked side parking lock mechanism will be explained.

FIG. 6 is a flow chart for operating the drive motor when outputting theactivation command to the unlocked side parking lock mechanism on thebasis of the motor rotation speed. This process starts when the motorrotation speed exceeds the predetermined rotation speed.

At step 11, the unlocked side drive motor is rotation-speed-feedbackcontrolled so that a target motor rotation speed becomes 0 (zero) or apredetermined value that is less than the predetermined rotation speed.However, the unlocked side drive motor might be controlled so that apreviously set certain torque is provided to the drive motor.

At step 12, a judgment is made as to whether or not an absolute value ofthe motor rotation speed of the unlocked side drive motor is less thanthe predetermined rotation speed. If the absolute value of the motorrotation speed of the unlocked side drive motor is less than thepredetermined rotation speed, it is judged that the motor rotation speedconverges and is less than the predetermined rotation speed, and theroutine proceeds to step S14. If the absolute value of the motorrotation speed of the unlocked side drive motor is not less than thepredetermined rotation speed, at is judged that the motor rotation speedis the predetermined rotation speed or more, and the routine proceeds tostep S13, then a diagnosis timer for the judgment of the motor rotationspeed convergence is reset. Also the routine returns to step S11, andthe rotation speed feedback control continues.

At step 14, count-up of the diagnosis timer for the judgment of themotor rotation speed convergence is done.

Subsequently, at step S15, a judgment is made as to whether or not acount value of the diagnosis timer exceeds a diagnostic time by which itcan be judged that the motor rotation speed converges. If it is judgedthat the count value of the diagnosis timer exceeds the diagnostic time,the routine proceeds to step S16, and the activation command isoutputted to the unlocked side parking lock mechanism. On the otherhand, if the diagnostic time does not elapse, the routine returns tostep S11, and the motor rotation speed control continues, also a checkof a convergence state of the motor rotation speed is continued.

FIG. 7 is time charts for operating the drive motor when outputting theactivation command to the unlocked side parking lock mechanism. Here, aninitial state of these time charts is a state in which the vehicle stopswith only the right side parking lock mechanism PLR activated.

At time t1, a check is made as to whether or not an absolute value ofthe motor rotation speed of the left side drive motor is less than thepredetermined rotation speed during a predetermined diagnostic time forwhich a predetermined vehicle stop state is diagnosed.

At time t2, when the absolute value of the motor rotation speed of therear left wheel RL is the predetermined rotation speed or more, thetorque is provided to the unlocked side left side drive motor ML, thenthe control is performed so that the rotation speed of the rear leftwheel RL decreases.

At time t3, when the motor rotation speed of the left side drive motorML is less than the predetermined rotation speed, a diagnostic time forthe judgment of the motor rotation speed convergence is set. Then, acheck is made as to whether or not the motor rotation speed absolutevalue of the left side drive motor ML is continuously less than thepredetermined rotation speed for the diagnostic time.

At time t4, when the absolute value or the motor rotation speed of thedrive motor ML is continuously less than the predetermined rotationspeed for the diagnostic time for the judgment of the motor rotationspeed convergence, the activation command is outputted to the left sideparking lock mechanism PLL, and the rear left wheel RL is locked. Atthis time, since the rotation is almost in a stop state when the parkingpole is engaged with the parking gear, the driver is not subject to theodd or awkward feeling.

Next, a process based on the cumulative motor rotation speed will beexplained.

FIG. 8 is a flow chart for operating the drive motor when outputting theactivation command to the unlocked side parking lock mechanism on thebasis of the cumulative motor rotation speed. This process starts whenthe cumulative motor rotation speed exceeds the predetermined cumulativemotor rotation speed.

At step S21, the unlocked side drive motor is rotation-speed-feedbackcontrolled so that a target motor rotation speed becomes 0 (zero) or apredetermined value that is less than a predetermined rotation speed.However, the unlocked side drive motor might be controlled so that apreviously set certain torque is provided to the drive motor.

At step S22, a judgment is made as to whether or not an absolute valueof the cumulative motor rotation speed of the unlocked side drive motoris less than a value that is obtained by adding a cumulativedifferential motor rotation speed to the predetermined cumulative motorrotation speed. If the absolute value is less than this new thresholdvalue obtained by the addition, it is judged that the movement of thevehicle is suppressed, and the routine proceeds to step S23. Here, thecumulative differential motor rotation speed is a value by which it canbe judged that the movement of the vehicle converges or settles by theproviding of the torque to the drive motor.

On the other hand, if the absolute value is not less than the newthreshold value, which means that the cumulative motor rotation speed isthe new threshold value or more, it is judged that a current state is astate in which the movement of the vehicle can not be suppressed even bythe rotation speed feedback control, and the routine proceeds to stepS25, then the activation command is immediately outputted to theunlocked side parking lock mechanism. With this process, the vehiclemovement is forcibly suppressed.

At step S23, count-up of a diagnosis timer for the judgment of thecumulative motor rotation speed convergence is done.

At step S24, a judgment is made as to whether or not a count value ofthe diagnosis timer exceeds a diagnostic time by which it can be judgedthat the cumulative motor rotation speed converges. If it is judged thatthe count value of the diagnosis timer exceeds the diagnostic time, theroutine proceeds to step S25, and the activation command is outputted tothe unlocked side parking lock mechanism. On the other hand, if thediagnostic time does not elapse, the routine returns to step S21, andthe motor rotation speed control continues, also a check of aconvergence state of the cumulative motor rotation speed is continued.

FIG. 9 is time charts for operating the drive motor when outputting theactivation command to the unlocked side parking lock mechanism on thebasis of the cumulative motor rotation speed. Here, an initial state ofthese time charts is a state in which the vehicle stops with only theright side parking lock mechanism PLR activated.

At time t1, a check is made as to whether or not an absolute value ofthe cumulative motor rotation speed of the left side drive motor is lessthan the predetermined rotation speed during a predetermined diagnostictime.

At time t2, when the absolute value of the cumulative motor rotationspeed of the rear left wheel RL is the predetermined rotation speed ormore, the torque is provided to the unlocked side left side drive motorML, then the control is performed so that the rotation speed of the rearleft wheel RL decreases. At this time, a diagnostic time for thejudgment of the cumulative motor rotation speed convergence is set, andalso the cumulative differential motor rotation speed is added to thepredetermined cumulative motor rotation speed, then this value is set asthe new threshold value. Then, a check is made as to whether or not thecumulative motor rotation speed absolute value of the left side drivemotor ML is continuously less than the new threshold value for thediagnostic time for the judgment of the cumulative motor rotation speedconvergence.

Then, at time t3 at which the diagnostic time for the judgment of thecumulative motor rotation speed convergence elapses, when the cumulativemotor rotation speed absolute value is less than the new thresholdvalue, the activation command is outputted to the left side parking lockmechanism PLL, and the rear left wheel RL is locked. At this time, sincethe rotation is almost in a stop state when the parking pole is engagedwith the parking gear, the driver is not subject to the odd or awkwardfeeling.

In view of the foregoing, the embodiment of the present inventionincludes the following configuration and effect.

(1) A parking lock control device of a vehicle has: a right side parkinglock mechanism PLR that is provided at a right wheel RR that is drivenby a drive motor MR (a right side motor); a left side parking lockmechanism PLL that is provided at a left wheel RL that is driven by adrive motor ML (a left side motor); a parking lock controller PLCU (aparking lock mechanism controller) that, when a parking lock activationcommand is outputted, activates either one of the parking lockmechanisms; and an inclination detecting unit 1, a present positiondetecting unit 2 and resolvers NR, NL (a vehicle behavior detectingunit) that estimate or detect a vehicle behavior in a case where onlythe one parking lock mechanism is activated. And the parking lockcontroller PLCU is configured to, when the vehicle movement is estimatedor detected and the vehicle moves a predetermined amount or more,generate a torque that suppresses the vehicle movement by the drivemotor connected to the other parking lock mechanism.

Accordingly, in a normal state, by activating only one parking lockmechanism, the power consumption can be suppressed, and the traveldistance can be made longer. Further, even if the vehicle moves in thestate in which only the one parking lock mechanism is activated, thevehicle movement can be suppressed by the operation of the drive motor.Thus, the odd or awkward feeling which the driver receives can besuppressed.

Here, a time when the one parking lock mechanism is activated could be aphase in which the activation command is outputted to the parking lockmechanism (i.e. before the one side is actually locked), or might be aphase after the parking pole is engaged with the parking gear by thefact that the parking lock mechanism is actually activated (i.e. afterthe one side is actually locked).

(2) The parking lock controller PLCU is configured to, when judged thatthe reticle movement is suppressed by the drive motor, activate theother parking lock mechanism.

Therefore, the other parking lock mechanism can be activated with thevehicle movement suppressed by the drive motor, thereby suppressing ashock that occurs upon the engagement of the parking pole and theparking gear. In addition, since the both parking lock mechanisms areactivated, even in a case where a force continuously acts on the vehiclein the vehicle moving direction due to the slope or inclination, thepower consumption by the motor drive can be suppressed.

Although the invention has been described above by reference to acertain embodiment of the invention, the invention is not limited to theembodiment described above. For instance, in the embodiment, as anexample, the rear wheel drive type electric vehicle is explained.However, the vehicle is not limited to this vehicle as long as eachwheel has the parking lock mechanism in a front wheel drive typeelectric vehicle or a four-wheel drive electric vehicle.

Further, in a casa where each of four wheels has the parking lockmechanism, configuration of the present invention is possible bycombination or the parking lock mechanism on one side of right and leftfront wheels and the parking lock mechanism, on the other side of rightand left rear wheels.

Furthermore, in the embodiment, when the driving wheel actually rotates,such torque as to suppress the rotation of the driving wheel is providedby the drive motor. However, the torque suppressing the rotation of thedriving wheel could be provided when the rotation of the driving wheelhas been predicted.

1. A parking lock control device of a vehicle comprising: a right sideparking lock mechanism that is provided at a right wheel that is drivenby a right side motor; a left side parking lock mechanism that isprovided at a left wheel that is driven by a left side motor; a parkinglock controller that, when a parking lock activation command isoutputted, activates either one of the parking lock mechanisms; and avehicle behavior detecting unit that estimates or detects a movement ofthe vehicle in a case where only the one parking lock mechanism isactivated, and the parking lock controller being configured to, when theestimated or detected vehicle movement is a predetermined amount ormore, generate a torque that suppresses the vehicle movement by themotor connected to the other parking lock mechanism.
 2. The parking lockcontrol device of the vehicle as claimed in claim 1, wherein: theparking lock controller is configured to, when judged that the vehiclemovement is suppressed by the motor, activate the other parking lockmechanism.
 3. The parking lock control device of the vehicle as claimedin claim 1, wherein: the vehicle behavior detecting unit detects thevehicle movement according to a rotation of the motor that correspondsto an unlocked side wheel.
 4. The parking lock control device of thevehicle as claimed in claim 1, wherein: the parking lock controllerperforms, to generate the torque, a rotation speed feedback control ofthe motor corresponding to the unlocked side wheel with a target motorrotation speed being 0 or a predetermined value that is close to
 0. 5. Amethod for controlling parking lock of a vehicle, the vehicle having aright side parking lock mechanism that is provided at a right wheel thatis driven by a right side motor and a left side parking lock mechanismthat is provided at a left wheel that is driven by a left side motor,the method comprising: when a parking lock activation command isoutputted, activating either one of the parking lock mechanisms;estimating or detecting a movement of the vehicle in a state in whichthe one parking lock mechanism is activated; and when the estimated ordetected vehicle movement is a predetermined amount or more, generatinga torque that suppresses the vehicle movement at the motor connected tothe other parking lock mechanism.